The object of the present invention is to provide means which permit continuously extruding and treating a product so as to subject each length of the product travelling through the installation to conditions of pressure, temperature and vibration frequency which modify the morphological structure and, hence, the physico-chemical properties of the product, by varying these conditions of pressure, temperature and frequency in accordance with a predetermined program so as to perform a continuous rheological treatment of the product.
It is to be noted that the morphological structure of the product is in particular defined by the degree of crystallinity, the texture, the type of crystals, the shape of the crystals, the size of the crystals, the elementary shape of the crystals, the interlamellar structure, the orientation determined by the nature of the bonds and the shape of the macromolecules and, in particular in the case of amorphous plastics, the "free volume", the total free volume and the structure of the free volume, these two factors determining the extent of internal strains existing in the product in the glassy state, and probably the ductility of the product.
The physico-chemical properties of the product are, in particular, its mechanical properties, that is to say its impact strength, ductility, modulus of elasticity, flow behavior and fatigue resistance.
The electrical properties are especially the breakdown voltage, the conductivity, the charge dissipation and the insulation resistance.
The thermal properties define are use temperature, the physical ageing resistance (if the material is heated) or its resistance to corrosion, oxidation and corrosive agents.
It is already known to modify the physico-chemical properties of a product by subjecting it to pressure, temperature and frequency variations in accordance with a program drawn up beforehand, which program depends on the variations to be achieved.
However, such operations are currently only carried out on samples of products and are not carried out continuously on a product in the shape of a tube, film or rod passing through an installation.
The object of the present invention is to provide means which make it possible to carry out such a treatment continuously.